There is known a conventional dog clutch gear in which engaging convex portions are provided on one of the opposite end surfaces of two gears adjacently installed on a rotating shaft and engaging concave portions meshing with the engaging convex portions are provided on the other. In addition, the gears are axially relatively shifted to allow the engaging convex portions and the engaging concave portions to engage with each other, thereby transmitting torque between the gears (see e.g. Japanese Patent Laid-open No. 2009-209950). The dog clutch gear described in Japanese Patent Laid-open No. 2009-209950 includes a rim portion having gear teeth on the outer circumferential portion; a boss portion fitted to a rotating shaft; and an annular wall portion connecting the rim portion with the boss portion and formed with engaging concave portions. In addition, the bottom wall of the engaging concave portion is provided with an oval weight-reduction hole so as to leave the bottom wall close to an engaging surface with the engaging convex portion.
A dog clutch gear 100 as illustrated in FIGS. 9 and 10 is known as a conventional dog clutch gear. This dog clutch gear 100 includes a rim portion 102 having gear teeth 101 on the outer circumference; a boss portion 103 fitted to a rotating shaft; an annular connecting portion 104 connecting the rim portion 102 with the boss portion 103; a plurality of engaging concave portions 105 formed on a lateral surface of the annular connecting portion 104 at circumferentially generally-regular intervals; and a plurality of ribs 106 each formed between the engaging concave portions 105, 105 adjacent to each other. Since the engagement between the ribs and engaging convex portions (not illustrated) transmits a rotational drive force, a large force is applied to the ribs 106.
In the conventional dog clutch gear 100, however, if an axial end surface 103 of the boss portion 103 is machined, a machined edge is formed at a joint portion 107 between the boss portion 103 and the rib 106. There is a possibility that stress concentration resulting from the transfer of the rotational drive force occurs at the machined edge. During the machining of the axial end surface 103a of the boss portion 103, also the plurality of ribs 106 each formed at circumferentially generally-regular intervals are subjected to cutting work. Therefore, a cutting load is intermittently applied to a cutting tool of a lathe or the like, which probably shortens the lifetime of the cutting tool.
A dog clutch gear is provided that can prevent stress concentration due to a machined edge from occurring in the dog clutch gear and that can prevent a cutting load from being intermittently applied to the cutting tool to lengthen the lifetime of the cutting tool.
A dog clutch gear includes a rim portion having power transmission teeth on an outer circumference; a boss portion fittable to a rotating shaft; an annular connecting portion connecting the rim portion with the boss portion; and a dog member formed on a lateral surface of the annular connecting portion, the dog clutch gear being engaged with the dog member of an adjacent gear, on the rotating shaft, to transfer a rotational force, is characterized in that a machined surface is formed on an axial end surface of the boss portion and in that a runout groove axially continuing from the dog member toward the axial end surface of the boss portion is formed at a joint portion between the boss portion and the dog member.
In addition, to the runout groove is formed to extend from the axial end surface of the boss portion toward an axial inside of said dog clutch gear.
In addition, the runout groove is formed to smoothly connect a circumferential lateral surface of the dog member with an outer circumferential lateral surface of the boss portion of the boss portion.
In addition a runout groove axially continuing from the dog member toward an axial end surface of the rim portion is formed at a joint portion between the rim portion and the dog member.
In addition, the runout groove is formed in a generally semicircular shape in cross-section, about a central axis of the dog clutch gear.
In addition, the runout groove is formed in a bowl shape in cross-section, about a central axis of the dog clutch gear.
In addition, the runout groove is formed to smoothly continue from a bottom thereof toward a circumferential lateral surface of the dog member.
In addition, the dog member side end surface forming part of the runout groove is formed to smoothly continue from an inner circumferential direction toward an outer circumferential direction.
The machined surface is formed on the axial end surface of the boss portion and the runout groove axially continuing from the dog member toward the axial end surface of the boss portion is formed at the joint portion between the boss portion and the dog member. Therefore, when the axial end surface of the boss portion is machined, the dog member will not be subjected to cutting work. In this way, since a machined edge is not formed at the joint portion, it is possible to prevent stress concentration due to the machined edge from occurring in the dog clutch gear, which can improve the durability of the dog clutch gear. Since the dog member is not subjected to cutting work, it is possible to prevent a cutting load from being intermittently applied to the cutting tool, which can lengthen the lifetime of the cutting tool.
The runout groove is formed to extend from the axial end surface of the boss portion toward the axial inside. Therefore, even if the axial end surface of the boss portion is machined with a large machining margin, the machined edge is not formed at the joint portion between the boss portion and the dog member. Thus, it is possible to prevent stress concentration due to the machined edge from occurring in the dog clutch gear, which can improve the durability of the dog clutch gear.
The runout groove is formed to smoothly connect the circumferential lateral surface of the dog member with the outer circumferential lateral surface of the boss portion. Therefore, it is possible to reduce stress applied to the runout groove, which can further improve the durability of the dog clutch gear.
The runout groove axially continuing from the dog member toward the axial end surface of the rim portion is formed at the joint portion between the rim portion and the dog member as well as at the joint portion between the boss portion and the dog member. Therefore, it is possible to prevent stress concentration from occurring at both ends of the dog member, which can further improve the durability of the dog clutch gear.
The runout groove is formed in a generally semicircular shape in cross-section, about the central axis of the dog clutch gear. Therefore, it is possible to reduce stress applied to the runout groove, which can further improve the durability of the dog clutch gear.
The runout groove is formed in a bowl shape in the cross-section, about the central axis of the dog clutch gear. Therefore, it is possible to reduce stress applied to the runout groove, which can further improve the durability of the dog clutch gear.
The runout groove is formed to smoothly continue from the bottom thereof toward the circumferential lateral surface of the dog member. Therefore, it is possible to reduce stress applied to the runout groove, which can further improve the durability of the dog clutch gear.
The dog member side lateral surface forming part of the runout groove is formed to smoothly continue from the inner circumferential direction toward the outer circumferential direction. Therefore, it is possible to reduce the number of places where stress concentration occurs.